Department of Biochemistry, Bose Institute, Kolkata, India.
PLoS One. 2012;7(5):e37468. doi: 10.1371/journal.pone.0037468. Epub 2012 May 23.
Virstatin is a small molecule that inhibits Vibrio cholerae virulence regulation, the causative agent for cholera. Here we report the interaction of virstatin with human serum albumin (HSA) using various biophysical methods. The drug binding was monitored using different isomeric forms of HSA (N form ∼pH 7.2, B form ∼pH 9.0 and F form ∼pH 3.5) by absorption and fluorescence spectroscopy. There is a considerable quenching of the intrinsic fluorescence of HSA on binding the drug. The distance (r) between donor (Trp214 in HSA) and acceptor (virstatin), obtained from Forster-type fluorescence resonance energy transfer (FRET), was found to be 3.05 nm. The ITC data revealed that the binding was an enthalpy-driven process and the binding constants K(a) for N and B isomers were found to be 6.09×10(5 )M(-1) and 4.47×10(5) M(-1), respectively. The conformational changes of HSA due to the interaction with the drug were investigated from circular dichroism (CD) and Fourier Transform Infrared (FTIR) spectroscopy. For 1:1 molar ratio of the protein and the drug the far-UV CD spectra showed an increase in α- helicity for all the conformers of HSA, and the protein is stabilized against urea and thermal unfolding. Molecular docking studies revealed possible residues involved in the protein-drug interaction and indicated that virstatin binds to Site I (subdomain IIA), also known as the warfarin binding site.
维司他汀是一种小分子，可抑制霍乱弧菌毒力调节，这是霍乱的病原体。在这里，我们使用各种生物物理方法报告了维司他汀与人血清白蛋白（HSA）的相互作用。通过吸收和荧光光谱法监测药物与不同异构形式的 HSA（N 型约 pH7.2、B 型约 pH9.0 和 F 型约 pH3.5）的结合。药物结合会导致 HSA 的本征荧光显著猝灭。从福斯特型荧光共振能量转移（FRET）获得的供体（HSA 中的色氨酸 214）和受体（维司他汀）之间的距离（r）为 3.05nm。ITC 数据表明，结合是一个焓驱动的过程，N 和 B 异构体的结合常数 K(a)分别为 6.09×10(5)M(-1)和 4.47×10(5)M(-1)。通过圆二色性（CD）和傅里叶变换红外（FTIR）光谱研究了 HSA 由于与药物相互作用而导致的构象变化。对于蛋白质和药物的 1:1 摩尔比，远紫外 CD 光谱显示所有 HSA 构象的α-螺旋度增加，并且蛋白质对尿素和热变性稳定。分子对接研究揭示了可能参与蛋白质-药物相互作用的残基，并表明维司他汀结合到 I 型位点（亚域 IIA），也称为华法林结合位点。
